For typical body-on-frame vehicles, the body is wider than the frame. In a side or lateral impact, the body sustains the initial impact and associated deformation. The body's floor crossmembers are the primary load paths for side impact protection in a first phase of the impact. With sufficient body deformation, frame structures are engaged and provide additional lateral load transfer. Due to a significant gap between the side of the body and the frame rails as found in typical body-on-frame vehicles, the floor crossmembers sustain the initial impact force alone. This requires significant body structure to achieve an appropriate structural strength to reduce undesired seat position shifts due to floor deformation.
The frame structure at present does not sustain any significant impact loading until the deformed body engages the proximate frame rail. No significant lateral load is transferred into or across the frame via the frame crossmembers until the deforming body engages the proximate frame rail.
While the body-to-frame mounts do transfer certain loads between the body and the frame, the intended and primary load transfer direction sustained by the mounts is in the vertical direction. Body mounts are not designed to transfer lateral impact loads from the body to the frame and enable a limited amount of lateral side to side movement of the body relative to the frame. Presently, brackets may be placed directly between the rocker panel and the side rail to transfer impact loading to the frame to achieve less body deflection, but these communicate the impact force solely from the rocker to the proximate frame rail, and allow for undesired or excessive deformation of the proximate frame rail.